Synthetic rubber compounding



Patented May 1, 1945 SYNTHETIC RUBBER GOMPOUNDIN Albert A. Somerville, Carmel, N. Y., assignor to R. T. Vanderbilt Co. Inc., New York, N. Y., a corporation of New York N Drawing. Application September 27', 1.943,

' Serial N 0. 504,055

4 Claims. (01. 260-42) My invention relates to improvements in the compounding and vulcanizing of synthetic rubbers produced by copolymerization of butadiene and styrene. This type of' synthetic rubber, to which I refer as synthetic rubber throughout this specification and in the claims, is illustrated by the product currently designated "GR-S rubber.

In some respects aging of vulcanized rubber compounds resembles in efiect continued curing, that is further vulcanization, of the compound. For example, a natural rubber compound vulcanized for a period less than optimum with an accelerator which is not fugitive under the conditions of vulcanization will, for an initial period,

tend to exhibit the same changes in properties as aging progresses that would have been exhibited as the result of longer cures. Thus, a vulcanized rubber compound might'be expected to exhibit, for example, increasing hardness and decreasing elongation at break with increasing age.

Natural rubber compounds, however, although following this tendency for a period depending upon the nature of the compound and the conditions of the cure, tend to exhibit, for example, decreasing hardness or a diminishing rate of increase in hardness and increasing elongation at break or a diminishing rate of decrease, in elongation at break as aging progresses. This characteristic of vulcanized natural rubber compounds is commonly designated reversion.

This property of vulcanized natural rubber compounds is of major importance with respect to their utility in a number of applications. This property of natural rubber in compounds vulcamzed with so-called persistent accelerators, accelerators which exhibit the eflect of a continuing cure at a very low rate in the vulcanized compound, permits the production of vulcanized compounds which exhibit extremely stable properties, extreme stability with respect to hardness and elongation at break forexample, over long periods of time. Thatis, in vulcanized natural rubber compounds which exhibit the property of reversion, persistent accelerators such as mercaptobenzothiazole and benzothiazyldisulphide, for example, can be used to balance this effect and thus to produce a vulcanized product exhibiting a high order of stability for long periods.

There are, as might be expected, other accelerators which tend toemphasize reversion, for example, the guanidines and the 'aldehydeamines and, in compounds containing limited proportions of sulfur, the dithiocarbamates and the thiurams. Synthetic rubber, however, does not exhibit this property of reversion, and this property is not imparted to vulcanized syntheticrubber commum properties, or an optimum value for some particular property, 'for a limited period as aging progresses, but stability for any prolonged period, with respectrto hardness and elongation at break, for example, cannot be obtained by the compounding and vulcanizing practices hitherto The utility of vulcanized synthetic available. I rubber compounds has been severely limited in many applications by this lack of any means to,

impart the property of reversion to such compounds. x

- -.I have discovered that the property of reversion can be imparted to vulcanized synthetic rubber compounds by including in the compound about 10%-20% by weight on the rubber of an aldolnaphthylamine alpha-naphthylamine,

and particularly aldol- My invention comprises vulcanized syntheticrubbercornpounds compris ing about 10%-20% by weight on the rubber of an aldolnaphthylamine, and particularly aldolalpha-naphthylamine and vulcanizable synthetic rubber compounds of such composition. My invention permits the production of vulcanized synthetic rubber compounds which exhibit, for exam ple, but small increases in hardness over long periods and in which relatively high values for elongation at break are well maintained. This important conjunction of properties has not to my knowledge been previously attained with vulcam'zed synthetic rubber compounds.

I have no explanation forthe result. Aldolalpha-na'phthylamine has been used as an antioxidant in natural rubber compounds for some timefbut in natural rubber compounds it exhibits no aging benefit in proportions above about 3%-4% by weight on the rubber and in such larger proportions it exhibits an excessive softening effect in natural rubber compounds. Although GR-S rubber, for example, contains about 2% by weight on the rubber of phenyl-betanaphthylamine or some similar anti-oxidant as a stabilizer, it does not exhibit the property of reversion. I have also tried large, proportions of a number of representative anti-oxidants with-- out securing the improved results of my invention. I have also tried the use of large proportions, separately, of aldol and .of naphthylamine without seeming comparable results. But I will tion at break of e much superior d containing no favorably Examples 111,

the compounds containing 10 doinaphthylamine exhibit unlongation at break which is ed compound containing aintained in the well-cured aged compounds. The values for elonga Example I.- Also,

parts or more of a1 aged a high initial e 'weil m these compounds after aging ar to those for the aged compoun aldolnaphthylamine and 'compare with those for the unag no aldolnaphthylamine; comparing IV and V with Example 1.

the compound of of the number oi I opposite each desi ongation in pounds per square inch appear under S," for tensile strength in pounds with which I have secured'the new results '01 my invention.

In the following tabulations 'of compounds.'

cures and physical properties,

each example was made up parts by weight indicated nated component, the cures were in aplaten.

press for periods varying from 15 minutes to 120 minutes as indicated under the temperature of cure, and, for each period of cure, the -10 values for stress at 300% e1 nwwmmm muss ncwwm e. n w 5 v Emhmm mmmmm mmmm m mmmmwmmmwm m. mfilwflm 1 m m. Tmmmm m -m m a wm m a s. a E E 1111 11111 W wmmmm mmmww SWWWA am M sham mmm mm wmsww m 1 n w mmmwm mamas m mmmm D m mmu mam m m wam m m mm mm mmwhm H nmmcwm uwwww w W Hw m m smmmww mwwmm M mwmmm wm. mn w M as a $9.1. w Tmmmmq swam. m m mw mm wa m mawmm m 1 am that n m uwm m .mwmmW mm umm awa so a n o e es a si is D mmwm m smmmwmmwmm mm- 5 0 G l E 0 5. 0 5 0 1 2 on m 5 o o twwmm wmm n. m mmmmm m mmmmm m .u h. m n. wwwv mw g rnet -m a hm as 0 m m m .mmm... a Wmpi, mww mmmwmmm m mm wmww m w w .smm mmmsmm m mmm r r c o l. mmw E is mum mmwu m wmm mmmmm w .m-Kn O t mwe O 9 afi mm mmm amm I H WMMW mmm mwfi mmmmmm w m mwmrmc w e m .m .55 a 12 loewn m wmn r .m m. mnmm w wms m m Tmmwwm s s mimmm m mm mmawm in m S E L111, 111?? mm 0 M mm 8 dm m m u. mmmdwmm mm smmmm :1; mm mmmhm dw mmmm mmmm spm o e m w. mm mmt ....d was. m a a mwmm 2% z m u .3%. s n mwwfwm We E stim m smhs w mfin 0 rain. t. .0 mbm mf. t. e e n MW t H Wm m mmsmmmw w m? w m. m mmmm flmsm sm mmmawmtm mm r m rs s M m .wc an t t e mmmmsmmmwam wwmmms m mmpmmmmmmmmmwmmmmmmmmmmmmmm ple with espectively, for the compound of upon aging.

pie, although eak decreased 450 nd 310 lbs. with a or the compound of Exam curing progresses is markedly better for the compound of Example VII. For exam the value for elongation at br lbs. with a 45-minute cure a 60-minute cure 1 VII, it decreased only 170 lbs. and 150 lbs.- the same cures, r Example part by weight per phthylamine. Comparthe difierences in hardand the aged samples of in the order of continued 5 the compound con- 1 ylamine but are 5, 3, 2 and advantage approximate 0.3-0.5

20 parts of the aldolna ng Examples VI and VII ness between the unaged the two compounds cure, are 20, 18, 13 and 12 for taining no aldolnaphth 1 forms compound containing 20 parts of aldol- Hnwmmwm u g mmmmm nmmw 1 r s 0050 r 5 5 m Emnmwmm mwmmmm muwwm m mama n .1 h 0 e n r .i. mw fiz f wmmm 11PM. ww5 52 m m m m mmmmmm awmmm m. 1 a. m 1 x 1 22221 I B t m E E m fia 9 1% $1; 1 1 fiww s 4 .1 I omf m. 1 21.11 H a QR S Homa e mummwm mm m mm mama m u 11.11 m Emmmmmm mmmmmm s m m m s a o 00 m t u m I u 5 o k mm w ww n wmuum m. mw t n I m m mw552 1 m e C 8 E m 1 LLLL. m 1 x 1222 22 1 1 1 1 22 a m m m m E 55 S e r. smfimmm mmmmm wh m. r r .14 111 m mu m mama Hmwmmwm ummmww mm, m w Wm x Emmmmmm mwm mm r .m o E mm x 5s t n I 1 1% 11 a? mmn .Q im wmmm t. 21 H m m mm m 5 L w mm m mm 8 m 1 1 1 1 m 1 x .1 212122122, 1 1 2 2 2 2 M e wtw m m0m E E E mmmm 3 w mmw 61% 9 G SW5 D 64mm 1 St E D 1 m 1 1 1 1 1 1 M 44.44. 7777 v Hammad A we w mm mm w m A mmmm m 5 5 0 m mmmmmn mmm m Wm w 5 a gu m m h 0M0 M0. 00 v e .m a mw m 1P. u n m m m m mo nm w. mwm eh We m m 1 1 1 1 m m 12 2 22 1 1 1 1 1. 2 m pm w u u n .E E 0 ;r t n smmummm mmmm em w w a n I 1 1 1 M r IM m n u n n m e. u u n mmmwww mam m m n n m I M et. n n m m m .m new hu an ammm m z m m I 0 r c 1 a m m n n m xm mmmwmm m m mm n u u n m m 2 2 1 1 1 1 1 2 k m u u u n n x o a m I u u n E m em aw I n n u e 1 n Z2 h v. i n n mm 1" m mme I mm"m a: 111 1 n 1 hm L :1 ww a mwmmw. m m mm 1... r a. .m m meow; a; m m g z z: m r th "flu M n Wyn D. u opo "n we imhh bb u Um .11. n M0 1 .I mluum .eflo. mmmmua momma d d y" I mmwmm n 33mm nmmmmm m w. m 1 m m mum m mrm m 1] h. l 8. Hm? mm 2 a m mu m m w 3111 1 muonn s'rnns'rnns'r'nns'rnn 420 2400 155 54 -450 2,050 550 54 525 1,140 525 55 455 1,050 125 51 545 2,500 505 54 415 2,120 55054 1,250 550 415 55 415 2,210 125 55 555 2,150 555 55 485 2,110 550 54 1,550 2,410 410 55 405 2,150 115 55 550 2,830 510 54 455 2,000 52 55 1,100 2,410 515 55 405 2,100 110 55 Example xxxm Example xxxw Example xxxv' Example xxx v1 GB-S rubber 100 100 -100 100 Channel carbon black 50 50 50 50 Zincoxide 5 5 5 5 Plasticizer 5 5 5 5 51011 2.5 5 4 Benzothlazyldisulphide... l. 5 l. 5 l. 5 1. 5 Diphenylguanidine .25 .25 .25 .25 Aldol-alpha-naphthylamin 20 20 20 UNAGED STEHST'EHSTEHS,T,EH 455- 2,220 150 55 510 1,550 505 51 5502400 510 1,150 2,500 510 545250055054 1,020 2550.500 51 4100 50054555 1,500 245045555 555 2,400 510 54 1,550 2,500 515 55 900 2,520 555 55 1,550 2,440 450 51 5552,55055054215024105105s 0202 ,450545501,2502,40044501 The foregoing Examplesxxlxandxxxshow alphanaphthylamine of rubber, for example, I

the general equivalence of aldolalphanaphthylamine and aldolbetanaphthylamine. Aldola lphanaphthylamine appears to be somewhat more effeotive in. diminishing the rate of increase in have found it advantageous toiuse about 2.5 parts by weight ofsulfur although this proportion is 40 somewhat larger than I would ordinarily use in a compound otherwise the same but omitting the be somewhat more effective in diminishing the rate of decrease in elongation at break as aging progresses.

The foregoing Examples xxm to XXXVI illustrate the eflect of variation in the proportion of sulfur. These results may also be compared with those of Examples I to VII in which somewhat lower proportions of sulfur are used. In a compound containing 20 parts by weight of 01001- cable to qR-s also illustrate the hardness and aldolbetanaphthylamine appearsto aldolalphanaphthylamine.

ltxamplomi 55mm nm'nxxm Example-XL 5 '5 5Hv 5,, 5 v 5 5" 5'. 5.; .n full The foregoing Examples XXXVI]: to XL illustrate the effect of aldolalphanaphthylamine in socalled sulfurless cures of synthetic rubber and advantage of'supplying some sulfur in addition to the vulcanizing agent required for vulcanization of the synthetic rubber. The compound of Example XXXVII is representative of the best rubber prior to my present invenof compounding practice appli- 6' tion. The improvement effected by including 20 parts by weight on the rubber of aldolalphanaphthylamine isshown by Example XXXVIII. The 7 further improvement effected by also including 0.3 part by weight on the rubber oi sulfuris shown by Example XL. Example is given to vulcanized synthetic rubber compounds compris-f ing about 10%-20% by weight on the rubber of an aldolnaphthylamlne and particularly aldolalphanaphthylamine, and the vulcanized products produced by vulcanization of such compounds. Such compounds I believe are the first or vulcanized synthetic rubber compounds to exhibit the important property of reversion in any practical sense. i v Iclaim: 1. A vulcanized butadiene-styrene copolymer synthetic rubber compound comprising about l0%-20% by weight on the rubber of an aldolnaphthylamine.

2. A vulcanized butadiene styrene copolymer synthetic rubber compound comprising about 10%-20% by weight on the rubber of aldolalpha-naphthylamine.

3. A vulcanizable butadiene-styrene copolymer synthetlcrrubber compound comprising about l0%-20% by weight naphthylamine.

4. A vulcanizable butadiene-styrene copolymer synthetic rubber compound comprising about on the rubber of an aldo- -10%-20% by weight on the rubber of aldolalpha-naphthylamine.

' ALBERT A. soimnvnm. 

